Chitinolytic properties of Bacillus pabuli K1

Abstract

The chitinolytic properties of Bacillus pabuli K1 isolated from mouldy grain was studied. Chitinase activity was measured as the release of p-nitrophenol from p-nitrophenyl-N,N'-diacetylchitobiose. Influences of substrate concentration and different environmental variables on growth and chitinase activity were determined. The optimum environmental conditions for chitinase production were: 30 degrees C, initial pH 8, initial oxygen 10% and aw > 0.99. Chitinase production was induced when B. pabuli K1 was grown on colloidal chitin. The smallest chito-oligosaccharide able to induce chitinase production was N,N'-diacetylchitobiose, (GlcNAc)2. Production was also induced by (GlcNAc)3 and (GlcNAc)4. When the bacterium was grown on glucose or N-acetylglucosamine, no chitinases were formed. The highest chitinase production observed was obtained with colloidal chitin as substrate. The production of chitinases by B. pabuli K1 growing on chitin was repressed by high levels (0.6%) of glucose. The production was also repressed by 0.6% starch, laminarin and beta-glucan from barley and by glycerol. The addition of pectin and carboxymethyl cellulose increased chitinase production.